Electromagnet coil assembly

ABSTRACT

An electromagnet coil assembly having a coil of wire wound on a spool, and an epoxy resin cover encapsulating the ends of the spool and the coil periphery. The wire winding can be of any typical configuration but can advantageously be a winding where a tap or taps are provided in the winding for using more than one voltage. A bracket includes first strip portions overlying the spool ends and the epoxy resin cover, and second strip portions extending between the first strip portions adjacent to and on opposite sides of the periphery of the epoxy resin cover. The epoxy resin cover on opposite sides of the first strip portions is exposed and has a pattern of relatively raised and lowered surfaces to promote radiation and convection of heat away from the coil. Preferably, the relatively raised and lowered surfaces are fins and intervening grooves respectively that are provided on and extend substantially the height of a substantially arcuate periphery of the exposed epoxy resin cover. In assembly with a valve, a tube is located within the spool, the tube extending between the first strip portions of the bracket and extending outwardly beyond the spool and one of the first strip portions. A plug, located in the tube, is adjacent to the other of the first strip portions. A pair of substantially T-shaped tubular shrouds are inserted in the spool, one at each end, the shrouds engaging the tube and the first strip portions of the bracket.

United StatesfPatent [191 Barbier et al.

[ June 18, 1974 ELECTROMAGNET COIL ASSEMBLY Inventors: William J. Barbier, St. Louis;

Thomas C. Knaebel, Kirkwood, both of Mo.

Sporlan Valve Company, St. Louis, Mo.

Filed: July 18, 1973 Appl. No.: 380,285

Related US. Application Data Continuation of Ser. No. 203,22l, Nov. 30, l97l, abandoned.

Assignee:

References Cited UNITED STATES PATENTS 4/l9l0 Larsen 317/156 3/1930 Hirt 3l7/l56 3/l959 Trought l74/DIG. 5 3/1963 Maxigiafico et al. 335/260 X 9/l969 Derbyshire et al. 336/61 Primary Examiner-Ge0rge Harris [57] ABSTRACT An electromagnet coil assembly having a coil of wire wound on a spool, and an epoxy resin cover encapsulating the ends of the spool and the coil periphery. The wire winding can be of any typical configuration but can advantageously be a winding where a tap or taps are provided in the winding for using more than one voltage. A bracket includes first strip portions overlying the spool ends and the epoxy resin cover, and second strip portions extending between the first strip portions adjacent to and on opposite sides of the periphery of the epoxy resin cover. The epoxy resin cover on opposite sides of the first strip portions is exposed and has a pattern of relatively raised and lowered surfaces to promote radiation and convection of heat away from the coil. Preferably, the relatively raised and lowered surfaces are fins and intervening grooves respectively that are provided on and extend substantially the height of a substantially arcuate periphery of the exposed epoxy resin cover. In assembly with a valve, a tube is located within the spool, the tube extending between the first strip portions of the bracket and extending outwardly beyond the spool and one of the first strip portions. A plug, located in the tube, is adjacent to the other of the first strip portions. A pair of substantially T-shaped tubular shrouds are inserted in the spool, one at each end, the shrouds engaging the tube and the first strip portions of the bracket.

4 Claims, 5 Drawing Figures .47 56 55 I 33- i I v64 36- 4o 41 46- '-62 E 63 Lt 1- PATENTED JUN l 3 I974 PEG. 5

FIG

FIG. 1

R E B R A B I. 3 M Tm NL EIL l mW THOMAS C. KNAE BEL CQR FMQQ- W FIG. 4

ATTORNEYS ELECTROMAGNET COIL ASSEMBLY This is a continuation of application Ser. No. 203,221, filed Nov. 30, 1971, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an improved encapsulating epoxy resin cover for promoting radiation and convection of heat away from the coil of an electromagnet coil assembly, and to the use of a novel multi-voltage winding which can be used with such cover having high heat dissipation abilities.

In the heretofore conventional coil arrangements utilizing a combined enclosure and flux return means for potted coils, the coil was not reliable because of the short insulation life attributed to high coil temperatures. In some devices, bum-outs were a problem because the plunger became jammed and could not enter the magnetic field to complete the ferrous circuit. The excessive heat caused by the lack of inductive coupling resulted in high current flows that caused coil bum-out. Moreover, the excessive heat was transmitted from the valve, with which the coil assembly is used, to the system, and thereby adversely afiected the system operation, particularly when the system was one of refrigeration. Moreover, an encapsulating thermo-plastic cover was subject to damage from impact. Furthermore, these prior coil assemblies suffered severe power loss in DC solenoid valves because of the inability to effectively dissipate the FR loss (resistive heating effect) and thereby operated at low pressure. Also prior coil assemblies, when applied to AC where iron losses are high, would not dissipate the FR loss in the winding thereby requiring a large build up of low resistance magnet wire to get sufficient turns. In addition, prior dual voltage coil assemblies required complex rewiring of two separate windings to obtain performance at the desired voltage. These coils had four leads which had to be wired and phased correctly. Generally they were limited 'to two voltages with a winding. Generally, dual voltage coils were wired in series for the higher voltage and in parallel for the lower voltage.

SUMMARY OF THE INVENTION The present electromagnet coil assembly provides a more reliable coil because of the longer insulation life available at the lower coil temperatures. Laboratory tests on this coil assembly demonstrated that the winding ran F. cooler at a minimum compared to the conventional coil and housing design it replaced.

There are no burn-out problems in the event the plunger cannot rise to close the magnetic air gap between the plunger and the top plug. Even if the plunger is jammed for some reason and cannot enter the magnetic field to complete the ferrous circuit, the heat caused by the lack of conductive coupling, resulting in high current flows, is dissipated effectively so that the coil can withstand these unusual conditions.

When the coil assembly is used on a valve incorporated in a refrigeration system, the heat transmitted to the system from the valve is reduced so that the operation of the system is not adversely affected.

The provision of fins on the encapsulating epoxy resin cover provides inherent impact protection since, in the event of a sharp impact, a fin will break on the outside edge or will chip, and thereby absorb the shock 2 and protect the body of the epoxy resin cover from damage.

A higher maximum operating pressure on DC solenoid coils are possible because of the tremendously improved ability of the coil assembly to dissipate the FR loss (resistive heating effect) which generally causes a severe power loss in DC solenoid valves. The weight of copper magnet wire can be significantly reduced on an AC coil assembly resulting in a significant construction economy because of the ability-of this coil assembly to dissipate 1 R loss in the windings. This is accomplished by using a smaller diameter magnet wire to make the required turns in the solenoid coil. The PR loss of the higher resistance magnet wire being dissipated by the large amount of exposed coil surface area. For example: A volt, 60 cycle coil with 2635 turns of No. 29 magnet wire and a resistance of 65 ohms will weigh .3 17 pounds. Equivalent performance can be obtained in a high heat dissipation coil, such as the one described here, with a winding consisting of 2730 turns of No. 32 magnet wire and a resistance of ohms with a weight of .153 pounds.

In addition this improved dissipation of FR winding heat in an AC coil can be utilized to produce a simpler and more economical form of multi-voltage coil. For example: A dual 120/240 volt AC coil can be constructed by modifying a 240 volt coil with a normal winding of 5260 turns of No. 32 wire with a tap at the 2730th turn. For 240 volt AC operation, the entire winding is wired into the circuit. For 120 volt AC operation the tap at the 2730th turn point and the common start lead are wired into the circuit. In this manner any number of different voltages could be tapped off this same coil.

The present invention includes as an article of manufacture a spool on which a coil of wire is wound, and

an epoxy resin cover encapsulating the wire coil about the coil periphery and at least partially covering the spool, the external periphery of the epoxy resin cover having a plurality of fins and intervening grooves to promote radiation and convection of heat away from the coil.

In an electromagnet coil assembly, the first strip portions of a bracket overlie the spool ends and epoxy resin cover, and second .strip portions extend between the ends of first strip portions adjacent the periphery of such epoxy resin cover. The leads from the magnet wire winding exit through the bracket for connection to a power supply. The epoxy resin cover on opposite sides of the first strip portions is exposed and is provided a pattern of relatively raised and lowered surfaces to promote radiation and convection of heat away from the coil. In the preferred embodiment, the surfaces are tins and intervening grooves extending substantially the height of the coil periphery.

In assembly, a tube of ferrous, non-magnetic mate rial such as austenitic stainless steel is located within a spool of an electrically insulating material, the tube extending between the first strip portions of a ferrous, magnetically conductive bracket and extending outwardly beyond the spool and one of the said first strip portions. A ferrous plug is located in and engages the tube, the plug adjacent and electrically connected to the other of said first strip portions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal, cross sectional view showing 3 the electromagnet coil assembly in association with a valve;

FIG. 2 is a top plan view of the coil assembly of FIG.

FIG. 3 is a fragmentary, side elevational view of the coil assembly as seen from the left of FIG. 1;

FIG. 4 is a cross sectional view of the coil assembly before it is mounted to the valve of FIG. I, and

FIG. 5 is a circuit diagram disclosing an AC multivoltage winding for use with this high heat dissipation coil assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now by characters of reference to the drawing, and first to FIG. 1, it will be understood that the electromagnet coil assembly generally indicated by can be used in association 'with a valve referred to by 11 that can be utilized in a line of a refrigeration system. Of course, the valve and the suggested usage is representative only, and is not limiting.

The valve 11 includes a body 12 with an inlet 13 and an outlet 14, and includes a valve seat 15 that defines a valve port placing the inlet 13 and outlet 14 in communication. An upstanding, circular flange 16 is provided on the body 12 about the valve seat 15 to provide a chamber 17.

Located within the cham ber 17 and slidably engaging the inside wall of body flange 16, is a valve member 20. A bleed hole 21, formed in the valve member 20, places that portion of chamber 17 on the top side of the valve member in communication with that portion of chamber 17 on the bottom side of the valve member 20 to provide a pressure equilibrium. Formed in the valve member 20 is a central, axial bore 22. A plastic disc 23 is carried by the valve member 20, the disc 23 seating on the valve seat 15 when the valve member 20 is located in its lowermost position, to close the valve port. For reasons which will later appear, the disc 23 is provided with a relatively small, axial aperture 24.

An elongate tube 25, formed of a ferrous, nonmagnetic mate rial such as austenitic stainless steel, has its lower end carried by a collar 26 that sits on and forms a seal with the top rim of flange 16. A cap 27 is disposed about the tube and is threadedly attached to the circular body flange 16 to clamp the collar 26 in sealing relation to the upper flange rim. The, valve 'member 20 includes a portion 30 that is slidably received in the lower end of tube 25.

The electromagnet coil assembly 10 includes a spool 31 formed of a plastic, electrically-insulating material and having end flanges 32. A coil 33 of wire is wound on the spool 31. Press-fitted into each end of the spool 31 is a substantially T-shaped, tubular shroud 34 formed of ferrous material such as steel. These shrouds 34 shape the magnetic field.

Molded over and about the wire coil 33 and at least partially over the spool end flanges 32 is an encapsulating epoxy resin cover 36. In molding the epoxy resin cover 36, such cover 36 is provided with a substantially flat peripheral surface 37. Diametrically opposite the flat surface 37, the epoxy resin cover is provided with an outstanding boss 40 through which extends the lead wires 41 connected to the wire coil 33. As will be seen best from FIG. 2, the encapsulating epoxy resin cover 36 has a substantially and generally circular configuration.

A bracket, generally indicated by 42, is formed of a ferrous, magnetically conductive material and includes opposed, first strip portions 43 overlying the top and bottom surfaces of the epoxy resin cover 36. More particularly, the first strip portions 43 extend diametrically across the epoxy resin cover 36 from the flat surface 37 to the boss 40, and engage the epoxy resin cover 36 overlying the spool end flanges 32 and the lateral collars 35 of the tubular shrouds 34. The lowermost strip portion 43 is provided with an aperture 44 aligned with and having substantially the same diameter as that of the associated tubular shroud 34. The uppermost strip portion 43is provided with a relatively smaller aperture The bracket 42 includes a pair of second strip portions 46 and 47 extending between the ends of the first strip portions 43 adjacent the periphery of the epoxy resin cover 36. One of the second strip portions 46 engages the flat surface 37 of the epoxy resin cover 36, and interconnects one pair of ends of the opposed first strip portions 43. This connection consists of end flanges 50 on the second strip portion 46 turned over and engaging the outer surfaces of the associated first strip portions 43, and tabs 51 formed on the ends of the first strip portions 43, located in and through slots formed in the second strip portion 46, and turned over against the outer side of such second strip portion 46.

The other second strip portion 47 is formed integrally with the opposite ends of the first strip portions 43, and is provided with an aperture 52 that is aligned with the cover boss 40 and through which the coil lead wire 41 extends.

In the preferred embodiment, a junction box 53 is carried by the bracket 42. The junction box 53 includes a circular fitting 54 that is located within the strip aperture 52 and peened over the second strip portion 47 to secure the box 53 to the bracket 42. This junction box 53 is utilized to make the'electrical connections. The junction box 53 is the typical form of electrical attachment. It could be left off completely or replaced with a conduit boss or other common types of electrical connectors. As is best seen in FIG. 1, the tube 25 is located within the spool 31, the tube 25 engaging the tubular shrouds 34. The tube 25 is provided with an integral in-turned end portion 55 that abuts the uppermost strip portion 43. Located within the tube 25 and engaging the intumed tube end 55 is an end plug 56 of ferrous material. The plug 56 is provided with an integral threaded member 57 that extends through the strip aperture 45. A name-plate washer 60 is fitted over the threaded member 57 and overlies the upper-most strip portion 43. A nut 61 is threadedly attached to the threaded member 57 and clamps the plug 56 and the tube 25 in assembly with the uppermost strip portion 43. Located within the tube 25 is a plunger or armature 62 formed of ferrous material. The plunger 62 carries an elongate valve pin 63, the pointed tip of which interfits the aperture 24 formed in the plastic disc 23. The opposite end of plunger 62 is recessed to receive a coil spring 64, one end of which engages the ferrous plug 56. The space between the plug 56 and the plunger 62 constitutes the magnetic gap.

lmportantly, the epoxy resin cover 36 on opposite sides of the first strip portion 43 is exposed and has a pattern of relatively raised and lowered surfaces to promote radiation and convection of heat away from the coil 33. These relatively raised and lowered surfaces are fins 65 and intervening grooves 66 respectively that extend substantially the height of the arcuate periphery of the exposed epoxy resin cover 36.

To operate this solenoid valve, the coil 33 is energized. The magnetic lines of force extend from the upper shroud 34 and tube to the uppermost strip portion 43, follow the second strip portions 46 and 47 to the tube 25, where they extend upwardly along the tube 25 and shrouds 34, and into the plunger 62 and plug 56 The magnetic field urges the plunger 62 upwardly to close the magnetic air gap between the plunger 62 and the plug 56 against the loading of spring 64. As the plunger 62 rises in the tube 25, the pin 63 opens the disc aperture 24, thereby causing a reduction in pressure above the valve member portion and thereby permitting the valve member 20 to rise in response to the unbalanced pressure. As the disc 23 disengages from the valve seat 15, the valve port is opened and thereby permits a flow between the inlet 13 and the outlet 14.

When the coil 33 is de-en'ergized, the loading of spring 64 urges the pin 63 into the disc aperture 24. The pressure above and below the valve member 20 is equalized and the valve member 20 is moved to close the valve port by seating the disc 23 on the valve seat 15.

The fins 65 and intervening grooves 66 promote the convection and radiation of heat away from the coil 33. The fins 65 on this coil design increase the exposed surface by approximately percent.

As a result of these fins formed on the epoxy resin cover 36, a more reliable coil operation is provided because of the longer insulating life available at the lower coil temperatures. Laboratory tests on this coil design demonstrates that the wire coil 33 runs 20F. cooler at a minimum compared to the conventional coil and housing design it replaced. Moreover, burn-out problems are eliminated in the event that the plunger 62 cannot rise to close the magnetic air gap between the plunger 62 and the top plug 56. On some solenoid valves, when the plunger is jammed for some reason and cannot enter the magnetic field to complete the ferrous circuit, the excessive heat caused by the lack of inductive coupling results in high current flows which cause coil burn-out. In this coil assembly, the heat can be dissipated by the fins 65 so that the coil 33 can withstand these unusual conditions. In addition, heat that is usually transmitted by the valve 11 to the system in which the valve is used, can adversely affect the operation of such system. But with this coil assembly, the heat transmitted to the system from the valve 11 is reduced since the heat is more effectively dissipated to the surrounding ambient by the fins 65 of the epoxy resin cover 36. Another advantage is realized in that the fins 65 provide inherent impact protection since, in the event of a sharp impact on the epoxy resin cover 36, a fin 65 will break on the outside edge or chip and thereby absorb the shock and protect the body of the epoxy resin cover 36 from damage. This particular coil assembly also permits a higher maximum operating pressure on DC solenoid coils because of the tremendously improved ability of the fins 65 of the epoxy resin cover 36 to dissipate the FR loss (resistive heating effect) which generally causes a severe power loss in DC solenoid valves.

Another advantage is a significant reduction in the amount of copper required for an AC coil because of the ability to. use higher resistance windings, dissipate the FR winding loss, and still meet insulation temperature limits. Manufacturing costs are reduced by this reduction in the weight of copper.

Using this ability to dissipate higher IR losses in AC coils, a much simpler and lower cost multi-voltage coil can be constructed by using low voltage taps at appropriate points in a series winding where the entire winding is used for the high voltage. In this manner a number of voltages such as AC, 200 AC, 208 AC, and 240 AC could be tapped off of one series winding. For

example, in FIG. 5, a series winding 33 is shown when the entire winding between the common tap A and end tap B is used for the high voltage, such as 240 AC, while that portion of the winding between common tap A and intermediate tap C is used for the low voltage such as 120 AC.

We claim as our invention:

1. In a direct attraction, multi-voltage, alternating current solenoid operator, comprising:

a. a spool,

b. an electrical coil of wire wound on the spool,

c. an epoxy resin cover completely encapsulating the ends of the spool and the coil periphery,

d. a magnetic bracket structure exposed directly to the ambient air, the bracket structure having first strip portions overlying the top and bottom surfaces of the epoxy resin cover, and having second strip portions extending between the first strip portions adjacent opposite peripheral portions of the epoxy resin cover,

e. the epoxy resin cover on opposite sides of said first strip portions being exposed directly to the ambient air and having a pattern of relatively raised and lowered surfaces to promote dissipation of the heat of the electrical coil by radiation and convection through the epoxy resin cover directly to the ambient air, and the wire coil is a series winding having a common tap at one end and a tap at the other end so that the entire winding between the common tap and end tap is used for high voltage AC, and having at least one intermediate tap so that the winding portion between the common tap and intermediate tap is used for relatively lower voltage AC.

2. In a direct attraction, multi-voltage, alternating current solenoid operator, comprising:

a. a spool,

b. an electrical coil of wire wound on the spool,

c. an epoxy resin cover completely encapsulating the ends of the spool and the coil periphery,

d. a magnetic bracket structure exposed directly to the ambient air, the bracket structure having first strip portions overlying the top and bottom surfaces of the epoxyresin cover, and having second strip portions extending between the first strip portions adjacent opposite peripheral portions of the epoxy resin cover, the heat of the iron losses and eddy current losses of the magnetic path being dissipated directly to the ambient air from the magnetic bracket structure,

e. the epoxy resin cover on opposite sides of said first strip portions being exposed directly to the ambient air and having a pattern of relatively raised and lowered surfaces to promote dissipation of the heat of the electrical coil by radiation and convection through the epoxy resin cover directly to the ambient air, and

. the wire coil is a series winding having a common tap at one end and a tap at the other end so that the entire winding between the common tap and end tap is used for high voltage AC, and having at least one intermediate tap so that the winding portion between the common tap and intermediate tap is used for relatively lower voltage AC.

3. In a direct attraction, multi-voltage, alternating current solenoid operator as defined in claim 2, in which:

g. the spool is of plastic, electrically insulating material,

h. the bracket structure is of a ferrous, magnetically conductive material,

i. a tube of a non-magnetic material is located within the spool, the tube extending between and engaging the said first strip portions of the bracket structure, and extending outwardly beyond the spool and one of said first strip portions,

j. a ferrous plug is located in and engages the tube,

current solenoid operator as defined in claim 3, in which:

1. the tube includes an in-tumed flange engageable and clamped by the plug against the said other of said first strip portions. 

1. In a direct attraction, multi-voltage, alternating current solenoid operator, comprising: a. a spool, b. an electrical coil of wire wound on the spool, c. an epoxy resin cover completely encapsulating the ends of the spool and the coil periphery, d. a magnetic bracket structure exposed directly to the ambient air, the bracket structure having first strip portions overlying the top and bottom surfaces of the epoxy resin cover, and having second strip portions extending between the first strip portions adjacent opposite peripheral portions of the epoxy resin cover, e. the epoxy resin cover on opposite sides of said first strip portions being exposed directly to the ambient air and having a pattern of relatively raised and lowered surfaces to promote dissipation of the heat of the electrical coil by radiation and convection through the epoxy resin cover directly to the ambient air, and f. the wire coil is a series winding having a common tap at one end and a tap at the other end so that the entire winding between the common tap and end tap is used for high voltage AC, and having at least one intermediate tap so that the winding portion between the common tap and intermediate tap is used for relatively lower voltage AC.
 2. In a direct attraction, multi-voltage, alternating current solenoid operator, comprising: a. a spool, b. an electrical coil of wire wound on the spool, c. an epoxy resin cover completely encapsulating the ends of the spool and the coil periphery, d. a magnetic bracket structure exposed directly to the ambient air, the bracket structure having first strip portions overlying the top and bottom surfaces of the epoxy resin cover, and having second strip portions extending between the first strip portions adjacent opposite peripheral portions of the epoxy resin cover, the heat of the iron losses and eddy current losses of the magnetic path being dissipated directly to the ambient air from the magnetic bracket structure, e. the epoxy resin cover on opposite sides of said first strip portions being exposed directly to the ambient air and having a pattern of relatively raised and lowered surfaces to promote dissipation of the heat of the electrical coil by radiation and convection through the epoxy resin cover directly to the ambient air, and f. the wire coil is a series winding having a common tap at one end and a tap at the other end so that the entire winding between the common tap and end tap is used for high voltage AC, and having at least one intermediate tap so that the winding portion between the common tap and intermediate tap is used for relatively lower voltage AC.
 3. In a direct attraction, multi-voltage, alternating current solenoid operator as defined in claim 2, in which: g. the spool is of plastic, electrically insulating material, h. the bracket structure is of a ferrous, magnetically conductive material, i. a tube of a non-magnetic material is located within the spool, the tube extending between and engaging the said first strip portions of the bracket structure, and extending outwardly beyond the spool and one of said first strip portions, j. a ferrous plug is located in and engages the tube, the plug being adjacent and connected to the other of said first strip portions in the same magnetic path, and k. a pair of substantially T-shaped tubular shrouds of ferrous material are inserted, one in each end of the spool, the shrouds overlying the spool ends, and engaging and holding the ends of the tube and engaging the adjacent said first strip portions.
 4. In a direct attraction, multi-voltage, alternating current solenoid operator as defined in claim 3, in which: 